Hello all my name is Gary and I have a 1992 Non turbo GTO. The car has been in storage for the last 7 years but I’ve got it running and it now has an MOT. The niggly problem that I have is it doesn’t idle as it should, its inclined to “hunt” a little bit and when your driving along and take your foot of the throttle at low speed the car starts to jerk about. The car accelerates away like a rocket and doesn’t misfire so I don’t think its an electrical problem. I think it is likely to be an air/fuel problem and that the poor idle and the jerking about is likely to be caused by the same issue. I have re set the throttle position sensor but it doesn’t appear to have made much difference. Is there anybody that has had a similar problem that can point me in the right direction? Thanks.
This is a common problem, often associated with faulty ecu, old fuel or sticky fuel pump. There are many other causes but I start with those 3 given that it been standing. Never adjust anything unless it is a replacement part or its been removed, because you now have to reset it in order to confirm what the fault is.
I think we can rule out old fuel because I have been driving it about for a couple of months and the tank has been filled several times. Fuel pump - could be, they are not too expensive, I could replace that. ECU. probably not the cheapest option and it’s not the original as I had to replace the ECU to get it started after 7 years. Any recommendations where I can get it looked at and its not going to cost me the price of a new car would be welcome? I totally agree don’t try and fix something if its not broken especially on these cars the problem is you sometimes try and fix things before you realise it’s not broken lol. As for the TPS I marked it all before I adjusted it so I can easily reset it to where it was. Thanks for your interest Joe. I was rather hoping someone would say I had that problem and this is what I did to fix it. Fingers crossed. 
As for the ECU get in touch with Ecu doctor https://the-ecu-doctor.co.uk/ they will check for issues first and report before they do any work.
Has the ecu been repaired previously? Which part of the country are you in?
The ECU hasn’t been repaired to my knowledge. I live in Dorset on the south coast. DT3
Thanks for your reply Spiros. I have contacted ECU Doctor and they want at least £260 for a rebuild and there is no guarantee that is what is causing the problem and I’m not sure the car is worth £260. There are other things that need doing on it not least a respray. It is getting close to where keeping the car on the road is going to cost more than it’s worth. I can see it ending up in that big scrap yard in the sky. 
Any body near You with a spare known working ECU to test ?
Not that I know of. Apart from mine I haven’t seen a GTO in years.
Hunting is usually a faulty stepper motor, it’s attached to the throttle body and controls idle speed, it’s got 4 coils, about 30 ohms each, often one of them ends up open circuit and you’ll get this very problem. Otherwise a faulty ecu temp sensor might cause it. It’s usually not an ECU problem
Thanks magn1t. I’ll look into it and let you know how I get on.
Hi all. Many thanks for all your comments. I finally got it sorted it was a faulty ECU. Car now idles fine at 700rpm. The jerking along at low revs has stooped and the poor starting when cold has been resolved and although I thought it sounded good when driving along it now sounds so much better. Many thanks to Joe 90 for all his help and support.
I’m in Bournemouth and have a mk2 im breaking …may be able to help with spares if you want some cheap bits …but breaker car is a turbo
Hi mate. I’m not sure what parts of the mk2 turbo are compatible with my mk1 non turbo but the only parts I’m looking for at the moment are the top of the door weather strips, new tyres and a center exhaust section.